Implement an explain feature

Author: kawasima

lib/core/src/__tests__/spec.test.js

@@ -26,3 +26,10 @@ describe('composing predicates', () => {
     expect(s.isValid(bigEven, 10000)).toBe(true);
   })
 });
+
+describe('explains', () => {
+  test('explain scalar', () => {
+    const bigEven = s.and(x => !isNaN(Number(x)), x => x%2 === 0, x => x > 1000);
+    const res = s.explain(bigEven, "foo")
+  });
+})

lib/core/src/base.js

@@ -34,6 +34,24 @@ class Spec {
   }
 }
 
+function dt(pred, x, form, cpred) {
+  if (!pred) return x;
+
+  return conform(pred, x);
+}
+
+function explainPredList(forms, preds, path, via, in_, x) {
+  let ret = x;
+  for (let i = 0; i < preds.length; i++) {
+    const nret = dt(preds[i], ret, forms[i]);
+    if (nret === INVALID) {
+      return specize(preds[i]).explain(path, via, in_, ret);
+    }
+    ret = nret;
+  }
+  return null;
+}
+
 class ScalarSpec extends Spec {
   constructor(form, pred, gfn, cpred) {
     super(gfn);
@@ -173,8 +191,12 @@ class ObjectSpec extends Spec {
   gen(overrides, path, rmap) {
     if (this.gfn) return this.gfn();
     const generators = {};
-    for (const k in this.predObj) {
-      generators[k] = gensub(this.predObj[k], overrides, [...path, k], rmap, this.predObj[k]);
+    for (const k in this.required) {
+      generators[k] = gensub(this.required[k], overrides, [...path, k], rmap, this.required[k]);
+    }
+    // TODO optional keys
+    for (const k in this.optional) {
+
     }
     return g.genObject(generators);
   }
@@ -183,7 +205,20 @@ class ObjectSpec extends Spec {
     if (typeof x !== 'object') {
       return [{path, via, pred: (x) => x === 'object', val: x, in: in_}];
     }
-    return null;
+    const explains = [];
+    for(let k in obj) {
+      const pred = this.optional[k] || this.required[k];
+      if (pred && !pred(obj[k])) {
+        explains.push({
+          path: [...path, k],
+          via,
+          pred,
+          val: x,
+            in: in_
+        });
+      }
+    }
+    return explains;
   }
 }
 

lib/testcheck/src/generators.js

@@ -74,7 +74,6 @@ function collDistinctBy_(emptyColl, keyFn, shuffleFn, gen, rng, size, numElement
   let s = size;
   for (let tries = 0; tries <= maxTries && numElements != res.length; tries++) {
     const v = callGen(gen, rng, size);
-    console.log(res);
     if (res.includes(v)) {
       s += 1;
     } else {
@@ -158,6 +157,7 @@ const generators = {
   get string() { return fmap(join, vector(this.char)) },
   get stringAscii() { return fmap(join, vector(this.charAscii)) },
   get stringAlphanumeric() { return fmap(join, vector(this.charAlphanumeric)) },
+  get stringAlpha() { return fmap(join, vector(this.charAlpha)) },
   get largeInteger() { return largeInteger_({}) },
 }
 

specs/basic/src/__tests__/basic.test.js

@@ -44,7 +44,7 @@ describe('generation', () => {
                                  x => gen.fmap(([s1, s2, s3]) => `${s1}@${s2}.${s3}`,
                                                gen.tuple(gen.generators.stringAlphanumeric,
                                                          gen.generators.stringAlphanumeric,
-                                                         gen.generators.stringAlphanumeric))))
+                                                         gen.generators.stringAlpha))))
       }
     });
     const res = gen.sample(s.gen(person));